DRV8811_15 Datasheet, PDF (14/32 Pages) Texas Instruments – DRV8811 Stepper Motor Controller IC

DRV8811
SLVS865I – SEPTEMBER 2008 – REVISED JANUARY 2015
Feature Description (continued)
PWM
ON
PWM
OFF
(t_OFF)
Winding
Current
RCx
Voltage
V_BLANK
V_DECAY
0.6 ×
VCC
0.21 × VCC
BLANK
FAST
(t_FD)
DECAY
SLOW
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R
VCC
0.6 × VCC
RCx
C
QS
QR
VBLANK
PWM_ON
ITRIP
BLANK
0.21 × VCC
PWM_OFF
PWM
DECAY
FAST_DECAY
To other PWM
Figure 8. PWM
8.3.4 Microstepping Indexer
Built-in indexer logic in the DRV8811 allows a number of different stepping configurations. The USM1 and USM0
pins are used to configure the stepping format as shown in Table 1:
Table 1. Microstepping Selection Bits
USM1
0
0
1
1
USM0
0
1
0
1
STEP MODE
Full step (2-phase excitation)
1/2 step (1-2 phase excitation)
1/4 step (W1-2 phase excitation)
Eight microsteps/steps
Table 2 shows the relative current and step directions for different settings of USM1 and USM0. At each rising
edge of the STEP input, the indexer travels to the next state in the table. The direction is shown with the DIR pin
high; if the DIR pin is low the sequence is reversed. Positive current is defined as xOUT1 = positive with respect
to xOUT2.
Note that the home state is 45 degrees. This state is entered at power-up or device reset. The HOMEn output
pin is driven low in this state. In all other states it is driven logic high.
FULL STEP
USM = 00
1/2 STEP
USM = 01
1
1
2
Table 2. Microstepping Indexer
1/4 STEP
USM = 10
1
2
3
4
1/8 STEP
USM = 11
1
2
3
4
5
6
7
8
AOUTx
BOUTx
CURRENT
CURRENT
(% FULL-SCALE) (% FULL-SCALE)
100
0
98
20
92
38
83
56
71
71
56
83
38
92
20
98
STEP ANGLE
(DEGREES)
0
11.325
22.5
33.75
45 (home state)
56.25
67.5
78.75
14
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